The present invention relates generally to the field of rail locomotives and more particularly to a method and apparatus for protecting a turbo-charged diesel locomotive engine from excessively high pressure in the combustion chamber.
It is known that excessively high pressure in the combustion chamber of an internal combustion engine can cause damage to the engine pistons, cylinder heads, and other components. The peak combustion chamber pressure is a function of the combustion process and the conditions of the incoming combustion air. The operation of a turbo-charger increases the peak combustion chamber pressure by increasing the temperature and pressure of the incoming air.
There are many known prior art arrangements for limiting the combustion chamber pressure. U.S. Pat. No. 4,655,040 issued on Apr. 7, 1987, to Parker discloses a relief valve (waste-gate valve) to bypass a portion of the engine exhaust gases around the turbine portion of a turbo-charger in order to limit the amount of pressure boost provided by the compressor portion of the turbo-charger. Waste gate valves are particularly expensive because they must be designed to operate in the harsh environment of the exhaust system.
U.S. Pat. No. 4,557,111 issued on Dec. 10, 1985, to Haussmann et al. discloses a control system for engaging and disengaging the operation of a turbo-charger. The apparatus of Haussmann is particularly useful for applications where the throttle setting of the engine is varied often. It is undesirable to utilize any system which cycles the turbo-charger on and off for applications where the engine operates for extended periods at a steady speed, such as in locomotive applications.
U.S. Pat. No. 4,434,761 issued on Mar. 6, 1984, to Ludwig teaches a fuel flow regulator which reduces the rate of flow of fuel to a diesel engine when the manifold intake air pressure is greater than a pre-determined value in order to protect the engine from an over-boost condition. It is undesirable to utilized a control system that decreases the fuel flow to a locomotive engine since the overall power production of the engine is a prime operating consideration.
U.S. Pat. No. 5,782,092 issued on Jul. 21, 1998, to Schultalbers et al. describes a control arrangement for a turbo-charger having a variable turbine geometry for controlling the output pressure of the compressor section of the turbo-charger. Variable turbine geometry turbo-chargers are expensive and are primarily beneficial in applications where the engine speed must be varied often, and where acceleration of the vehicle is a primary consideration. As such, the apparatus of Schultalbers is not particularly well suited for application to a turbo-charged diesel locomotive engine.